/*java jdk 1.7+
# -*- coding: utf-8 -
'''
Created on 2020年05月10日
@author: zxyong 13738196011
'''*/

package com.zxy.common;

public final class Base64
{
	private static final int	BASELENGTH				= 128;
	private static final int	LOOKUPLENGTH			= 64;
	private static final int	TWENTYFOURBITGROUP		= 24;
	private static final int	EIGHTBIT				= 8;
	private static final int	SIXTEENBIT				= 16;
	private static final int	FOURBYTE				= 4;
	private static final int	SIGN					= -128;
	private static char			PAD						= '=';
	private static byte[]		base64Alphabet			= new byte[BASELENGTH];
	private static char[]		lookUpBase64Alphabet	= new char[LOOKUPLENGTH];

	static
	{
		for(int i = 0;i < BASELENGTH;++i)
		{
			base64Alphabet[i] = -1;
		}
		for(int i = 'Z';i >= 'A';i--)
		{
			base64Alphabet[i] = (byte) (i - 'A');
		}
		for(int i = 'z';i >= 'a';i--)
		{
			base64Alphabet[i] = (byte) (i - 'a' + 26);
		}

		for(int i = '9';i >= '0';i--)
		{
			base64Alphabet[i] = (byte) (i - '0' + 52);
		}

		base64Alphabet['+'] = 62;
		base64Alphabet['/'] = 63;

		for(int i = 0;i <= 25;i++)
		{
			lookUpBase64Alphabet[i] = (char) ('A' + i);
		}

		for(int i = 26,j = 0;i <= 51;i++,j++)
		{
			lookUpBase64Alphabet[i] = (char) ('a' + j);
		}

		for(int i = 52,j = 0;i <= 61;i++,j++)
		{
			lookUpBase64Alphabet[i] = (char) ('0' + j);
		}
		lookUpBase64Alphabet[62] = (char) '+';
		lookUpBase64Alphabet[63] = (char) '/';

	}

	private static boolean isWhiteSpace(char octect)
	{
		return(octect == 0x20 || octect == 0xd || octect == 0xa
				|| octect == 0x9);
	}

	private static boolean isPad(char octect)
	{
		return(octect == PAD);
	}

	private static boolean isData(char octect)
	{
		return(octect < BASELENGTH && base64Alphabet[octect] != -1);
	}

	/**
	 * Encodes hex octects into Base64
	 * 
	 * @param binaryData
	 *            Array containing binaryData
	 * @return Encoded Base64 array
	 */
	public static String encode(byte[] binaryData)
	{

		if(java.util.Objects.equals(binaryData,null))
		{
			return null;
		}

		int lengthDataBits = binaryData.length * EIGHTBIT;
		if(lengthDataBits == 0)
		{
			return "";
		}

		int fewerThan24bits = lengthDataBits % TWENTYFOURBITGROUP;
		int numberTriplets = lengthDataBits / TWENTYFOURBITGROUP;
		int numberQuartet = fewerThan24bits != 0 ? numberTriplets
				+ 1 : numberTriplets;
		char encodedData[] = null;

		encodedData = new char[numberQuartet * 4];

		byte k = 0, l = 0, b1 = 0, b2 = 0, b3 = 0;

		int encodedIndex = 0;
		int dataIndex = 0;

		for(int i = 0;i < numberTriplets;i++)
		{
			b1 = binaryData[dataIndex++];
			b2 = binaryData[dataIndex++];
			b3 = binaryData[dataIndex++];

			l = (byte) (b2 & 0x0f);
			k = (byte) (b1 & 0x03);

			byte val1 = ((b1
					& SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2
							^ 0xc0);
			byte val2 = ((b2
					& SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4
							^ 0xf0);
			byte val3 = ((b3
					& SIGN) == 0) ? (byte) (b3 >> 6) : (byte) ((b3) >> 6
							^ 0xfc);

			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[(l << 2) | val3];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[b3 & 0x3f];
		}

		// form integral number of 6-bit groups
		if(fewerThan24bits == EIGHTBIT)
		{
			b1 = binaryData[dataIndex];
			k = (byte) (b1 & 0x03);

			byte val1 = ((b1
					& SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2
							^ 0xc0);
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[k << 4];
			encodedData[encodedIndex++] = PAD;
			encodedData[encodedIndex++] = PAD;
		}else if(fewerThan24bits == SIXTEENBIT)
		{
			b1 = binaryData[dataIndex];
			b2 = binaryData[dataIndex + 1];
			l = (byte) (b2 & 0x0f);
			k = (byte) (b1 & 0x03);

			byte val1 = ((b1
					& SIGN) == 0) ? (byte) (b1 >> 2) : (byte) ((b1) >> 2
							^ 0xc0);
			byte val2 = ((b2
					& SIGN) == 0) ? (byte) (b2 >> 4) : (byte) ((b2) >> 4
							^ 0xf0);

			encodedData[encodedIndex++] = lookUpBase64Alphabet[val1];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[val2 | (k << 4)];
			encodedData[encodedIndex++] = lookUpBase64Alphabet[l << 2];
			encodedData[encodedIndex++] = PAD;
		}

		return new String(encodedData);
	}

	/**
	 * Decodes Base64 data into octects
	 * 
	 * @param encoded
	 *            string containing Base64 data
	 * @return Array containind decoded data.
	 */
	public static byte[] decode(String encoded)
	{

		if(java.util.Objects.equals(encoded,null))
		{
			return null;
		}

		char[] base64Data = encoded.toCharArray();
		// remove white spaces
		int len = removeWhiteSpace(base64Data);

		if(len % FOURBYTE != 0)
		{
			return null;// should be divisible by four
		}

		int numberQuadruple = (len / FOURBYTE);

		if(numberQuadruple == 0)
		{
			return new byte[0];
		}

		byte decodedData[] = null;
		byte b1 = 0, b2 = 0, b3 = 0, b4 = 0;
		char d1 = 0, d2 = 0, d3 = 0, d4 = 0;

		int i = 0;
		int encodedIndex = 0;
		int dataIndex = 0;
		decodedData = new byte[(numberQuadruple) * 3];

		for(;i < numberQuadruple - 1;i++)
		{

			if(!isData((d1 = base64Data[dataIndex++]))
					|| !isData((d2 = base64Data[dataIndex++]))
					|| !isData((d3 = base64Data[dataIndex++]))
					|| !isData((d4 = base64Data[dataIndex++])))
			{
				return null;
			}// if found "no data" just return null

			b1 = base64Alphabet[d1];
			b2 = base64Alphabet[d2];
			b3 = base64Alphabet[d3];
			b4 = base64Alphabet[d4];

			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4)
					| ((b3 >> 2) & 0xf));
			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);
		}

		if(!isData((d1 = base64Data[dataIndex++]))
				|| !isData((d2 = base64Data[dataIndex++])))
		{
			return null;// if found "no data" just return null
		}

		b1 = base64Alphabet[d1];
		b2 = base64Alphabet[d2];

		d3 = base64Data[dataIndex++];
		d4 = base64Data[dataIndex++];
		if(!isData((d3)) || !isData((d4)))
		{// Check if they are PAD characters
			if(isPad(d3) && isPad(d4))
			{
				if((b2 & 0xf) != 0)// last 4 bits should be zero
				{
					return null;
				}
				byte[] tmp = new byte[i * 3 + 1];
				System.arraycopy(decodedData,0,tmp,0,i * 3);
				tmp[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
				return tmp;
			}else if(!isPad(d3) && isPad(d4))
			{
				b3 = base64Alphabet[d3];
				if((b3 & 0x3) != 0)// last 2 bits should be zero
				{
					return null;
				}
				byte[] tmp = new byte[i * 3 + 2];
				System.arraycopy(decodedData,0,tmp,0,i * 3);
				tmp[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
				tmp[encodedIndex] = (byte) (((b2 & 0xf) << 4)
						| ((b3 >> 2) & 0xf));
				return tmp;
			}else
			{
				return null;
			}
		}else
		{ // No PAD e.g 3cQl
			b3 = base64Alphabet[d3];
			b4 = base64Alphabet[d4];
			decodedData[encodedIndex++] = (byte) (b1 << 2 | b2 >> 4);
			decodedData[encodedIndex++] = (byte) (((b2 & 0xf) << 4)
					| ((b3 >> 2) & 0xf));
			decodedData[encodedIndex++] = (byte) (b3 << 6 | b4);

		}

		return decodedData;
	}

	/**
	 * remove WhiteSpace from MIME containing encoded Base64 data.
	 * 
	 * @param data
	 *            the byte array of base64 data (with WS)
	 * @return the new length
	 */
	private static int removeWhiteSpace(char[] data)
	{
		if(java.util.Objects.equals(data,null))
		{
			return 0;
		}

		// count characters that's not whitespace
		int newSize = 0;
		int len = data.length;
		for(int i = 0;i < len;i++)
		{
			if(!isWhiteSpace(data[i]))
			{
				data[newSize++] = data[i];
			}
		}
		return newSize;
	}
}